1. Field of the Invention
The present invention relates to a communication apparatus and a method for controlling the communication apparatus.
2. Description of the Related Art
In a wireless communication performed between two apparatuses, if a wireless resource (e.g., time or frequency) is allocated beforehand for each of transmission processing and reception processing, the wireless communication may not be performed efficiently. Therefore, for example, IEEE802.11 wireless local area network (hereinafter, wireless LAN) uses a method for acquiring a transmission right on a “first come, first served” basis in a case where no carrier is detected. This method is generally referred to as Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA).
Near Field Communication (NFC) and TransferJet (registered trademark) are examples of recently available non-contact communication (close proximity wireless communication). According to this kind of non-contact communication, a communication distance is very short. Only when two communication devices are located close to each other (e.g., within 10 cm for NFC or within 3 cm for TransferJet™, a wireless link can be established (connected) for data transmission/reception to be performed between two communication devices. If two communication devices are separated far from each other, the wireless link is disconnected.
The data communication between two communication devices according to TransferJet™ is presumed to be performed in one-to-one fashion, as described in a publicly available whitepaper (see “TransferJet™ Overview Whitepaper” TransferJet Consortium, 2009), which can be obtained from a pre-designated website introducing some use cases (e.g., http://www.transferjet.org/tj/transferjet_whitepaper.pdf). This whitepaper also describes data sharing between two users, which can be realized when their devices are located close to each other.
For example, to realize the data sharing using TransferJet™, according to an example method, a user performs an operation for selecting transmission data on a user's device and then brings the user's device close to a communication partner's device to start data communication. However, according to the non-contact communication such as TransferJet™, if the distance between two devices slightly exceeds the communication area, the wireless link is immediately disconnected. Therefore, user's performing the above described operation for selecting the transmission data while maintaining the wireless link is generally difficult. However, the above described whitepaper describes nothing about how to control data transmission and reception processing in a case where two devices are brought close to each other after the transmission data selection in each device is completed.
CSMA/CA is a method similar to the wireless LAN, which is usable as a data communication control method applicable in the above described case. According to CSMA/CA, data transmission processing begins on the “first come, first served” basis. However, in this case, if one device acquires a transmission right, the other device cannot start its own data transmission before the device that acquired the transmission right completes the data transmission.
For example, if a communication partner's device is earlier in starting data transmission than the user's device, data transmission from the user's own device does not start immediately or smoothly and therefore the user may misunderstand that the data transmission was failed. As a result, the user may unnecessarily move the user's device or may repeat the operation for retransmitting the data.
Further, in a case where a message indicating completion of the data reception is displayed at timing when data reception from the communication partner's device has been completed, the user who saw the reception completion message may misunderstand that data transmission from the user's own device has been also completed and may move the user's device away from the communication partner's device.